The low viscosity of many rubber polymerizates, especially of the ethylene vinylacetate or ethylene acrylate type, obtainable from present day production facilities, promote many processing problems during the conversion to finished components which makes their use impracticable for many of these applications. Such problems include sticking to the surfaces of processing equipment, insufficient rigidity during extrusion and low mass/bulk pressure during molding.
During the manufacture of rubber polymerizates, it has been noted that the gel content of such materials was maintained at a very low level in order to preserve a workable safety margin during subsequent processing steps; significantly less than 20% by weight being normal. During vulcanization of the polymerizates, the gel content was strongly enhanced by chemical (usually sulfur based) and/or free radical crosslinking induced by radiation treatment or peroxide cure systems.
For example, the radiation polymerization of elastomers is described in detail by W. Hofmann, "the Rubber Technology Handbook", pages 403 to 406, published in Munich, Vienna, N.Y., 1989. In addition, polymerization with high energy rays is described in "the Handbook for Vulcanization and Vulcanization Additives", pages 359 to 363, (BAYER AG, Leverkusen, 1965). Unfortunately, the polymerizates produced based on the state of the art are frequently very poorly workable in the usual rubber processing equipment.